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The term radiated emissions refers to the unintentional release of electromagnetic energy from an electronic device. The electronic device generates the electromagnetic fields that unintentionally propagate away from the device’s structure. In general, radiated emissions are usually associated with non-intentional radiators, but intentional radiators can also have unwanted emissions at frequencies outside their intended transmission frequency band. As was discussed in the EMC Regulations module, the allowable radiated emissions from electronic modules are regulated by various organizations and agencies. Electronic devices that have significant amounts of radiated emissions may interfere with their normal operation or the normal operation of other devices in close proximity. For these reasons, it is important to understand the concepts behind the origins of radiated emissions so that fundamental design techniques can be used to minimize the emissions. This module will investigate the origins of radiated emissions, and discuss methods to predict, measure, and minimize the radiated emissions from an electronic device. Differential and common mode currents will be introduced, and their roles in radiated emissions will be investigated. Using current probes to measure the differential and common mode currents on current carrying wires will be discussed. Finally, a discussion will be given on the role of circuit geometry and device structure on the radiated emissions from an electronic device.

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